The extravehicular activity (EVA) requirements for Space Station Freedom and future long-duration space missions demand advanced technologies for the life support subsystems in the astronaut portable life support system (PLSS). A NASA-funded program is currently underway to develop a full-scale, breadboard, regenerate metal oxide carbon dioxide (CO2) removal system. This technology is a promising concept to replace the lithium hydroxide absorber presently used for removing CO2 in the recycled breathing gas in the PLSS, but cannot be efficiently regenerated to be used for another EVA mission.In the metal oxide carbon dioxide removal system, an “active” metal oxide compound, contained within a solid absorbent material, effectively removes the CO2 by chemically reacting to form a metal carbonate during astronaut EVA. The absorbent is then regenerated thermally, by decomposing the resulting carbonate and thereby releasing CO2, to reform the metal oxide. This regenerate CO2 removal system, which can be used for many EVA missions, will reduce expendables and logistics requirements associated with the method presently used for CO2 removal.This paper discusses the factors which must be considered in selection of a metal oxide absorbent for CO2 removal for space applications, and the laboratory tests performed on metal oxide absorbent materials which were developed during the first phase of the program. These tests include both characterization studies and dynamic CO2 uptake and regeneration measurements. The preliminary design of the breadboard system, which performs both the absorption and regeneration functions, is also presented.